Former Howard government minister Mal Brough says he was not involved in any conspiracy against Parliament Speaker Peter Slipper.

Mr Slipper has continuously denied claims he misused taxi dockets or that he sexually harassed his former staff member James Ashby.

Mr Ashby has filed a civil case against Mr Slipper, and federal police are investigating the Cabcharge misuse claims.

Mr Brough is seeking Liberal National Party pre-selection to run against Mr Slipper in the seat of Fisher at the next federal election.

Mr Brough has confirmed he and his wife met Mr Ashby three times before the allegations were made public.

He says he was extremely sceptical at first because Mr Ashby was working for Mr Slipper at the time.

"I consulted with my wife and we agreed that we would find out what he wanted but we would do it together so that we'd have a witness," he told AM.

"That's how concerned we were about meeting with anyone connected with Mr Slipper's office.

"We were very aware, right from the start, that sooner or later it would become clear that he and I had met and that the Labor Party and perhaps some elements of the media would try and make it out to be some sort of conspiracy or whatever.

"But the fact is is that if you're going to assist someone then and you should come to the judgment that they're in a world of pain and under enormous stress well I'm afraid it's not an option to walk away."

The former Indigenous affairs minister says he gave Mr Ashby a number of pieces of advice.

"If you're going to pursue these issues you had better make sure you're on solid ground, that you're telling the whole truth, you'll have the weight of the Government, the media and Mr Slipper's office down on you," he said.

"You need solid legal advice. I can't provide that to you and if you believe a crime is being committed I think the only right thing to do is approach the police."

Mr Brough says he did not provide Mr Ashby with a lawyer.

"He sought that on his own. I did not provide him with the Harmer Lawyers, I did not make him the connection to the Harmers Lawyers, I wasn't even aware of them," he said.

Labor frontbencher Craig Emerson claims the meeting is further evidence the Coalition has been intimately involved in airing the allegations against Mr Slipper.

"It is inconceivable that a former senior minister in the Howard government would have told no one else about this when he himself has dramatically changed his story," he said.

"People are lying here. And this is what we've been saying - that there is a cover-up."